Even more so than sushi, Japanese season and cook rice in a variety of ways, collectively callled
takikomi gohan. I've been going basic lately, since I've gotten lazy over the years with a variety of store-bought packs, both wet and dry, that I just dump into the cooker, and turn on. Like the one below, which is very basic (the soy & sake combo) and traditional. Of course, I don't use matsutake, though. Every house has its own recipe and ingredients (some pre-cooked leftovers with complementary taste work well). You can experiment with grains other than white, sticky short-grain.
Matsutake Gohan
1. Marinate/rehydrate thin bite-size mushroom pieces in following, or equivalent: 1 Tbsp soy sauce, 1 Tbsp sake rice wine, 1 tsp instant dashi stock powder. 10 minutes might be enough. Discard any marinade which did not soak into the mushrooms.
2. Mix the mushrooms into the rice. The liquid is essentially the same as the marinade. So. for say 3 cups of rice, my liquid will be about: 3-1/3 cup room temp dashi stock, 2 tablespoons sake, 2-1/2 tablespoons soy sauce, and a pinch of salt. Cook.
Some people cook the rice first, and then fold in the marinated mushrooms. Some skip the marinade all together and dump raw shrooms into the mix. Either way, it’s tasty. Don’t overdo the soy sauce; regular dark soy is fine, it will have a pleasing brown color.
It's a good starch base for bento. As you can see, I had been thinking of mushrooms lately.
Gyoza potstickers. Some pickled veggies. White miso soup.